1. Field of the Invention
The present invention relates to a centrifugal fan, and more particularly to a centrifugal fan improved to reduce the noise.
2. Description of the Prior Art
Generally, the conventional centrifugal fan as shown in FIG. 1(a) is composed of a frame 10, a motor 20 and an impeller 30. Among these, the frame 10 includes a intake 11 and an outlet(not shown). The motor 20 mounted to the frame 10 is used to rotate the impeller 30. The impeller 30 further includes a hub 31, a bottom plate 32 and a plurality of blades 33 formed thereon.
Still referring to FIG. 1(a), the blades 33 urge the inlet air from the a flow path parallel to the axis of the impeller 30, outward radially away from the hub 31. However, such the conventional centrifugal fan suffers the problem that the noise caused by the uneven inlet airflow passing through the intake 11 and the impeller 13.
Another conventional centrifugal fan as shown in FIG. 1(b) is composed of a frame 10, a motor 20 and an impeller 30. Among these, the frame 10 includes two inlets including a first intake 11 and a second intake 12, and an outlet (not shown). A plurality of ribs 13 are formed in the second intake 12. The motor 20 mounted to the frame 10 is used to rotate the impeller 30. The impeller 30 further includes a hub 31, a bottom plate 32 and a plurality of blades 33 formed thereon.
However, the drawbacks of the conventional centrifugal fan are as follows. First, the inlet airflow through the first intake 11 and that through the second intake 12 interferes with each other and the disturbance as well as the noise thus occur. Furthermore, the noise occurs during the blades 33 cross the rib 13.
Therefore, there is a need in the art for solving the above-mentioned problems.
The object of the present invention is to reduce the noise of a centrifugal fan. The object of the present invention is achieved by (1) isolating the inlet airflow through the first intake and the inlet airflow through the second intake so as to eliminate the disturbance; (2) enlarging the interval between the first intake and the impeller so as to smooth the inlet airflow; and (3) providing the structure that the second blade and the rib form an intersection angle of about 90 degree as the second blade crosses the rib.
The centrifugal fan of the present invention comprises a frame, a rotatory means and an impeller. Among these, the frame has a first intake, a second intake, at least one air outlet (not shown) and a plurality of ribs. The rib crosses the second intake. The rotatory means such as a motor, mounted in the frame is used to rotate the impeller.
The impeller further includes a hub, a partition, a plurality of first blades and a plurality of second blades. Among these, the hub is coupled to the rotatory means such that the impeller can be rotated by means of the rotatory means. The partition extends outward along the radial direction of the hub so as to isolate the inlet air of the first intake and that of the second intake and thus reduce noise.
Additionally, the partition further has a first surface and a second surface opposite to each other. A plurality of first blades are formed on the first surface. The first blades are separated form the hub. That is, the first blades do not directly connect with the hub. Similarly, a plurality of second blades are formed on the second surface. The second blades are separated form the hub. That is, the second blades do not directly connect with the hub. The second blade and the rib form an intersection angle of about 90 degrees as the second blade crosses the rib. Therefore, the noise is reduced.
It should be noted that each of the first blades or the second blades selectively includes a cut corner formed thereon. In the first blades, the cut corner is adjacent to the edge of the first intake. In the second blades, the cut corner is adjacent to the edge of the second intake. In this manner, the interval between the first intake and the impeller is enlarged so as to reduce noise. Further, the first blades may be arranged asymmetrically or symmetrically with respect to the second blades.